Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$224.44	4.490%	$234.5174	$234.52	$234.50	$234.50
Purchase #2	$35.90	4.131%	$37.383	$37.38	$37.40	$37.40
Purchase #3	$38.64	8.222%	$41.817	$41.82	$41.80	$41.80
Purchase #4	$51.84	9.544%	$56.7876	$56.79	$56.80	$56.80
Purchase #5	$212.82	12.173%	$238.7266	$238.73	$238.75	$238.70
Purchase #6	$237.25	12.702%	$267.3855	$267.39	$267.40	$267.40
Purchase #7	$203.44	10.220%	$224.2316	$224.23	$224.25	$224.20
7 purchase totals =	$1,004.33		$1,100.8487	$1,100.86	$1,100.90	$1,100.80